New European research has found that parents who take longer to get pregnant and who use fertility treatment may have children with a higher risk of developing asthma.
Carried out by Norwegian and UK researchers, the new large-scale study looked at data gathered from a total of 550,199 children. Children were defined as having asthma if they had used asthma drugs in the 12 months before they turned 7 years old.
The researchers also gathered data on parents’ fertility treatment, time to conception, number and timing of any previous miscarriages, and other potentially influential factors such as mother’s age, asthma, smoking during pregnancy, and weight before pregnancy.
The findings, published online in the journal Thorax, showed that children who had been conceived with the help of fertility treatment were up to 42% more likely to have asthma than children whose parents didn’t undergo any treatment.
However, when the children born as a result of fertility treatment were compared to those who were spontaneously conceived after more than 12 months, they were just 22% more likely to have asthma.
The number of a woman’s previous miscarriages was also associated with an increased risk of asthma, with one miscarriage linked with a 7% increased risk of the condition, and three or more linked to a 24% heightened risk, although this was only found for miscarriages which occurred during the first 12 weeks of pregnancy.
The researchers commented that this suggests that poor fertility alone does not explain the increased asthma risk among the children conceived with the help of fertility treatment,
As an observational study the researchers note that the findings cannot establish a cause and more research is now needed.
However, the findings are in line with those from previous studies, which have also suggested that children conceived with the aid of fertility treatment may be more prone to asthma.
It is still not clear whether it is the fertility treatment itself of factors associated with subfertility which may contribute to the increased risk.